One form of connector that is widely used in the field of telecommunications is the RJ45 type of connector comprising a modular jack for receiving a compatible modular plug that terminates four twisted wire pairs. These connectors are used both in active telecommunications equipment, for example routers, and passive equipment, for example patch panels.
An RJ45 jack has an array of eight contacts at its front side, conventionally numbered 1 to 8, for engagement with respective contacts in the plug. As is well-known, contacts 4 and 5 of the jack are conventionally for connection to a first wire pair on the jack side, contacts 1 and 2 are for connection to a second wire pair, contacts 3 and 6 are for connection to a third wire pair, and contacts 7 and 8 are for connection to a fourth wire pair. In other words, in this type of connector, there is conventionally a region in the array of contacts in which adjacent contacts (i.e. contacts 3 to 6) belong alternately to different wire pairs while, in the remainder of the array, each pair of adjacent contacts (i.e. contacts 1, 2 and 7, 8) belongs to one respective wire pair.
It is known that unwanted crosstalk is mainly created by the plug and front contacts of the jack, especially between the inner wire pairs connected to contacts 3 to 6 of the jack. The amount of crosstalk increases with increasing operating frequency and as the number of connectors occupying a particular space is increased. It may even reach a level at which it interferes with, or prevents, the transmission of data.
The jack of a telecommunications connector conventionally includes a printed circuit board (PCB) on which the connectors may be mounted and through which they are connected to the incoming wire pairs, and it has previously been proposed to implement crosstalk compensation on this PCB (see, for example, WO 2005/064755 (Panduit Corp.); US 2008/0090468 (Reeves et al); and U.S. Pat. No. 6,464,541 (Hashim et al)).
It has also previously been proposed to reduce crosstalk introduced by the mechanical parts of a telecommunications connector by modifying the shape of the front contacts of the jack. This can, however, result in front contacts that have an undesirably complicated shape, or are difficult to assemble and maintain in the required position within the jack, or do not accept and engage consistently with the variety of mating plugs available on the market.
US 2002/0132532 (Henneberger) describes a modular jack of the RJ45 type in which the front contacts have three different geometric configurations, two of the configurations being described as “rearwardly extending” and one of the configurations being described as “forwardly extending”. The described configurations are said to assist in reducing crosstalk between the contacts located at positions 3 to 6 of the jack. In another configuration, described in U.S. Pat. No. 6,120,330 (Gwiazdowski), the jack contacts are crossed for the purpose of crosstalk compensation.
It is also desirable, in a telecommunications connector, to have an effective and consistent contact force between the contacts of the jack and those of any mating plug inserted into the jack, across the variety of plugs that is typically available on the market.